5个PHP性能优化的编程习惯

<script src="ajax.js"></script>
<form>
<table>
<tr>
  <td>用户名：</td>
  <td><input type="text" id="txt1" onKeyUp="showHint(this.value)"></td>
 </tr>
 <tr align="center">
  <td colspan="2"><span id="txtHint"></span></td>
 </tr>
</table>
</form>

var xmlHttp
function showHint(str)
{
if (str.length==0)
  {
  document.getElementById("txtHint").innerHTML=""
  return
  }
xmlHttp=GetXmlHttpObject()
if (xmlHttp==null)
  {
  alert ("Browser does not support HTTP Request")
  return
  }
xmlHttp.onreadystatechange=stateChanged

var geturl="conn.php?q="+str
//sid是增加一个随机数 防止页面启用缓存技术·
geturl=geturl+"&sid="+Math.random()
geturl=encodeURI(geturl);
geturl=encodeURI(geturl);
xmlHttp.open("GET",geturl,true)
xmlHttp.send(null)
}
function stateChanged()
{
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
 {
 document.getElementById("txtHint").innerHTML=xmlHttp.responseText
 }
}
function GetXmlHttpObject()
{
var xmlHttp=null;
try
 {
 // Firefox, Opera 8.0+, Safari
 xmlHttp=new XMLHttpRequest();
 }
catch (e)
 {
 // Internet Explorer
 try
  {
  xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
  }
 catch (e)
  {
  xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
 }
return xmlHttp;
}

<?php
$q=$_GET["q"];
$q = urldecode($q);

if (strlen($q) > 0)
{
  $conn = @mysql_connect("localhost","root","1010") or die ("MySql连接错误");
  mysql_select_db("xin",$conn);
  mysql_query("set names 'utf8'");
  
  $sql = "SELECT username FROM message WHERE username = '$q'";
  $query = mysql_query($sql);
  @$row = mysql_fetch_array($query);
  
  if(!empty($row['username']))
  {
   $response = "<font color=red>已经被注册！</font>";
  }else
  {
   $response = "<font color=blue>恭喜！可以注册！</font>";
  }
  
  echo $response;
}

?>

DROP DATABASE IF EXISTS `xin`;
CREATE DATABASE `xin` /*!40100 DEFAULT CHARACTER SET utf8 */;
USE `xin`;

CREATE TABLE `message` (
  `id` int(11) NOT NULL auto_increment,
  `username` varchar(20) default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

$imgs = array();
$imgs[0] = '1.jpg';
$imgs[1] = '2.jpg';
$imgs[2] = '3.jpg';
$imgs[3] = '4.jpg';
$target = 'emp.jpg';//背景图片
$target_img = Imagecreatefromjpeg($target);
$source= array();
foreach ($imgs as $k=>$v){
    $source[$k]['source'] = Imagecreatefromjpeg($v);
    $source[$k]['size'] = getimagesize($v);
}
//imagecopy ($target_img,$source[0]['source'],2,2,0,0,$source[0]['size'][0],$source[0]['size'][1]);
//imagecopy ($target_img,$source[1]['source'],250,2,0,0,$source[1]['size'][0],$source[1]['size'][1]);
$num1=0;
$num=3; //控制列数，一行几列，0为1以此类推。
$tmp=2;
$tmpy=2; //图片之间的间距
for ($i=0; $i<4; $i++){
    imagecopy($target_img,$source[$i]['source'],$tmp,$tmpy,0,0,$source[$i]['size'][0],$source[$i]['size'][1]);
    $tmp = $tmp+$source[$i]['size'][0];
    $tmp = $tmp+5;
    if($i==$num){
        $tmpy = $tmpy+$source[$i]['size'][1];
        $tmpy = $tmpy+5;
        $tmp=2;
        $num=$num+3;
    }
}
Imagejpeg($target_img,'pin.jpg');
?>

<img src="pin.jpg">

<?php
function is_exist($str,$key){
 foreach($key as $v){
  if(strpos($str,$v)>-1){
   return true;
  }
 }
 return false;
}
$str = 'abcdefg我们中国';
$key = array('4','5','a');
if(is_exist($str,$key)){
 echo 'YES';
}
else{
 echo 'NO';
}
?>

<?php
ignore_user_abort(); // 关掉浏览器，PHP脚本也可以继续执行
set_time_limit(600); // 设置程序的执行时间为600秒
// set_time_limit(0); // 设置程序的执行时间为无限长
$interval = 5; // 每隔5秒运行

do {
    $fp = fopen('sjyhome.txt', 'a'); // 打开 sjyhome.txt
    fwrite($fp, '欢迎来到SJY之家 www.111cn.net'); // 往 sjyhome.txt 写入信息
    fclose($fp); // 关闭 sjyhome.txt
    sleep($interval); // 等待5秒
} while (true);
?>